Recording materials utilizing color development caused through a reaction between a color former and a color developer are widely used as thermal recording paper for outputting/recording by a facsimile, a printer or the like, as pressure sensitive copying paper for simultaneously making a plurality of document copies, or the like, because recording processing may be conducted with such recording materials without performing complicated processing such as developing and fixing processing in a short period of time by using a comparatively simple apparatus. Such recording materials are desired to rapidly develop a color, retain whiteness in a portion with no color developed (hereinafter referred to as the “background”) and obtain a color developed image with high fastness, and from the viewpoint of long-term storage stability, particularly a recording material excellent in light resistance of the background is demanded. Therefore, various efforts have been exerted to develop color former, color developer, stabilizer and the like, but a sufficiently satisfactory recording material well-balanced in dynamic sensitivity, storage property for a background and an image and the like has not been found yet.
Although 2,4′-dihydroxydiphenylsulfone and 4-hydroxy-4′-isopropoxydiphenylsulfone are conventionally known as recording materials excellent in storage property for a background, the light resistance of the background attained by them is not satisfactory yet.
The present inventors have already proposed a recording material excellent in light resistance of a background and using a cinnamic acid amide-based compound as a color developer (see patent document 1), but obtained crystal of this compound is colored in yellow and hence is not sufficiently satisfactory, and thus, a practical recording material has not been attained yet.